In the ceramic tiles industry, much effort is invested in developing technologies and methods for producing ceramic tiles with a desired pattern. The industry has moved from producing tiles with the desired pattern only on the top layer or only on the surface layer to producing tiles with the desired pattern running through the entire thickness of the tile.
One of the known methods of doing this is by loading dry soil powder inside a container and then discharging the content through the opening of discharging tubes attached to the container into a vertical compartment, forming layers of soil powder of different types and colors the vertical compartment. The vertical compartment is then rotated 90 degrees to transfer the layers of soil powder to a horizontal mold. The layers of soil power are then pressed together under high pressure, creating a ceramic tile. The various characteristics of the layers of different of soil powders, such as colors and texture, translate into the tile pattern. However, the problem associated with this method is that there are difficulties with controlling the amount of soil powder released into the compartment, resulting in an inability to regulate and vary the width of color band. Thus, the patterns that can be obtained are limited. In addition, the rotation of the vertical compartment causes the soil granules to shift, resulting in distortion of the pattern. Thus, the obtained tiles must be subjected to further surface treatment after firing to reveal the pattern.
European Patent No. EP1273408 and International Publication No. WO2004071733 disclosed a technique to make continuous veining of patterns extending through the entire thickness of tiles or slabs. However, there remains the possibility that materials on the surface layer will mix together, causing the desired pattern to be distorted. There has been, therefore, a necessity to remove those mixed materials at the surface layer by suction before pressing in order to obtain patterns that are visible without having to polish the upper surfaces of ceramic tiles after firing.
European Patent EP 1334811 disclosed a technique for making patterns throughout the mass of the ceramic tiles which is characterized by a double-pressing that comprises of first a low pressure compacting. The compacted ceramic tiles are subsequently decorated by an ink-jet system to apply, according to the design, special ceramic colors which can penetrate into the tile mass. This technique, however, results in patterns in the tile mass that are somewhat blurred or incomplete. Further, the penetration of the ceramic colors is not deep enough to create a pattern in the lower layers of the tile mass.
All the known methods and apparatuses above comprise the compacting of material in powdery form.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.